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The density and the distribution of lesser noctule (Nyctalus leisleri) can be conditioned by
the structural heterogeneity and the availability of cavities in the wooden habitat. On the
other hand, ecological factors as the trophic availability or the protection from predators
probably are also conditioned by the forest structure. At the same time, wood structures
depend on the management made on the forests. In order to answer these questions, the
structure of beeches forests has been specialized in relation to relevant parameters for the
use of nest boxes and noctule population has been sampled in different structures of beech
forests in North–East of Catalonia. Therefore, it has determined the activity by means of
inspection of nest boxes. They have been reviewed periodically in summer, winter and
autumn during 2006 and 2014 a total of 382 nest boxes localized in different kind of beech
forests. The results we got in the characterization of the different beech forests show a big
contrast between them depending on the management to what they are being subjected :
It is evident a decrease in structural heterogeneity and availability of cavities in immature
beech woods and defectives. Whereas the results obtained for the taxes of occupation
show an increase of the activity of the nest boxes in diminishing the maturity of the forests
masses. It has been observed how the mature beech forests and the mature under
silvicultural management, registered some taxes of low activity, whereas beech clarified
woods and coppice woods registered a much higher occupancy rates. It has been observed
also as a good forest specialist, the small noctule tends to occupy much more boxes located
inside the forest, probably in search of greater thermal comfort and protection from
predation. The maturity of the forests and, consequently, the management done on them,
can influence in the distribution of lesser noctule on a wider geographic scale as it could be
in a massif or in a country.
It is recommended to focus the forest management of the beech woods of Catalonia on a
way to promote the density of big trees with cavities in the trunk, as well as the
interspecific heterogeneity and vegetative layers. It also presents as a valid alternative to
try to stabilize the populations of small noctules, the location of nest boxes in beech forests
where the natural shelter are scarce
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